I was feeding them to Blaze when she was still around 7-9". She eventually stopped eating them (and that's good, cuz she was eating a lot of them). I would feed about 30 or so a day, so I would go through 2 cups in a week. She would probably eat more of them, if I offered them to her. I fed them at lunch and crix at dinner.
You don't need to dust them with calcium powder if you feed them exclusively. They are packed with calcium. If you feed crix, continue to dust them 5x weekly. BUT! You do need to dust them with the vitamin powder 2x weekly.